Ever-increasing usage of the Internet is expected to lead to even higher demands on the capacity of Internet routers than those which already persist today. However, the rate of growth of traffic through a given Web site or traffic point in the Internet may vary considerably amongst different Internet Service Providers (ISPs). In some cases, the growth may be sudden and staggering, requiring huge increases in capacity on an almost instantaneous basis. In other cases, an anticipated increase in capacity might still be some time away, although a router with a basic switching capacity may need to be purchased immediately in order to satisfy an existing demand.
A conventional approach to upgrading the routing capacity through a given traffic point is to simply replace the existing router with a new, higher-capacity device. The old router is either decommissioned or relegated to a less traffic-intensive area of the ISP's internal network. Unfortunately, this approach requires a significant capital expenditure on the part of the ISP, since higher-capacity routers tend to be disproportionately more expensive than lower-capacity routers. Moreover, a capital expenditure of this nature is necessitated each time a capacity increase is required or desired. Additional disadvantages include the “down time” associated with installation of a new router, testing of new connections, changing suppliers and so on.
Clearly, it would be advantageous to provide a scalable solution to the problem of accommodating traffic growth through a router. However, as now described, conventional router design makes this a near impossible feat. Specifically, a scalable router typically has two or more chassis, each of which contains multiple switch cards and line cards. The line cards have ports for interfacing with an external network. Internally to the router, the switch cards are connected to the line cards and to one another by a backplane on each chassis, and by direct interconnections across multiple chassis.
In order to enhance the available switching capacity of the router, it may appear plausible to add one or more extra chassis but it should also be apparent that these additional chassis must somehow be connected to the existing chassis. As a result, existing hardware connections, both within and between he existing chassis, must be disconnected and then re-connected according to a different inter-chassis topology and a different intra-chassis interconnect pattern. Thus, while avoiding part of the capital expenditure associated with an outright replacement of the existing router, the conventional solution has the disadvantage of requiring added installation and testing efforts, both of which are labour-intensive and prone to error.
Hence, there remains a strong need in the industry to provide a scalable router that would be designed to accommodate changes in capacity without requiring replacement or disconnection of the existing inter-chassis or intra-chassis connection hardware.